This invention relates to an absorption refrigerator and the method of the producing the same, and more particularly, to an absorption refrigerator having two absorbers and two evaporators arranged in a two-stage manner which can pump up heat from low temperature to high temperature with a large temperature difference.
An example of an absorption refrigerator is shown in the Japanese Paten Laid-open 59-18355/1984 that has two absorbers and two evaporators arranged in a two-stage manner and that is capable of pumping up heat with the large temperature difference. The absorption refrigerator shown in this prior art has a low temperature evaporator and a low temperature absorber besides an evaporator and an absorber that are provided in an conventional absorption refrigerator. Refrigerant liquid condensed in a condenser evaporates and vaporizes in the evaporator, then the refrigerant vapor is absorbed into a concentrated solution in the absorber. A part of the refrigerant liquid which did not evaporate in the evaporator evaporates in the low temperature evaporator, then it flows into the low temperature absorber. As a result, it is absorbed into a middle concentrated solution which is the diluted solution.
Another example of the absorption refrigerator is described in the Japanese Patent Laid-open 4-268171/1992 that has absorbers arranged in a two-stage manner and that is capable of pumping up heat with the large temperature difference. This absorption refrigerator provides a mid-absorption room and a mid-evaporation room between an evaporation room and an absorption room. In a heating mode, refrigerant liquid condensed in a condenser is introduced to the evaporation room, and the refrigerant liquid that could not evaporate in the evaporation room is introduced to the mid-evaporation room. That is, the refrigerant liquid flows into the evaporation room and the mid-evaporation room in series.
There is an advantage that the absorption heat pump shown in the Japanese Patent Laid-open 59-18355/1984 can pump up heat from the low temperature to the high temperature because of having a two-stage type evaporator-absorber. The solution in the low temperature absorber absorbs the refrigerant vapor and rises its temperature in the absorption refrigerator. This solution is conducted to the high temperature evaporator through a bypassed return conduit of the refrigerant liquid. This causes the temperature difference for heat transfer to be large and the performance of an absorption cycle to be low because the refrigerant temperature at a discharge of the absorber is higher than the evaporation temperature of the refrigerant. In addition, the pumping power for circulating the refrigerant from the evaporator to the absorber it is also needed.
By the way, the refrigerant liquid is supplied from the evaporator room of lower temperature side to the mid-evaporating room of higher temperature side sequentially in heating operation in the Japanese Patent Laid-open 4-268171/1992. Thus, the absorption cycle can be used even in the heating operation. However, this absorption refrigerator does not work as an absorption refrigerator having absorbers and evaporators arranged in a two-stage manner but works as a conventional absorption refrigerator having single stage absorber in the cooling operation. Thus, it can not pump up cold below 0.degree. C. This absorption refrigerator transports heat from the mid-absorption room to the mid-evaporation room with heat pipes. The temperature difference for heat transport may become larger and the performance of the absorption cycle will be degenerated. It is needed that both of the temperature difference between the solution and the substances in the heat pipes and the temperature difference between the substances in the heat pipes and the refrigerant vapor are larger than the temperature difference that the heat exchange can occur. Therefore, it is desired that the absorption refrigerator is free from the above inconveniences.